字符串Scala中的模式匹配

Question

I wrote the code above to define the type of String based on some rules.

def dataType (input:String) : String = input match {
  case input if input.startsWith("Q")   => "StringType";
  case input if (input.startsWith("8") && !(input.contains("F"))) => "IntegerType"
  case input if (input.startsWith("8") && (input.contains("F"))) => "FloatType"
  case _                             => "UnknowType";
}

This code works well , but I want to optimize it by avoiding the use of If satements. I want it to be based on pattern matching only without any use of if statements. I tried to modify it this way , but it gives me bad results :

def dataType (input:String) : String = input match {
  case "startsWith('Q')"  => "StringType"
  case "startsWith('8') && !(contains('F')))" => "IntegerType"
  case "startsWith('8') && (contains('F')))" => "FloatType"
  case _                             => "UnknowType";
}

it always gives me the UnknownType result

Any help with this please

Best Regards

Answer 1

Since you are checking for the initial letter and boolean for containing F , you can create Tuple2[Char, Boolean] of those cases and use it in you match case as following

def dataType (input:String) : String = (input.charAt(0), input.contains('F')) match {

  case ('8', true) => "FloatType"
  case ('Q', _)  => "StringType"
  case ('8', false) => "IntegerType"
  case _ => "UnknowType"
}

And you should be fine